By combining observations of the distant Universe made with ESA's Herschel andPlanck space observatories, cosmologists have discovered what could be the precursors of the vast clusters of galaxies that we ...

Designed to detect the fossil radiation of the universe, the Planck satellite, working in tandem with Herschel, can also help to understand the macrostructure of the universe. A just-published experimental ...

NASA's Aqua satellite captured an image of Typhoon Maysak as it strengthened into a super typhoon on March 31, reaching Category 5 hurricane status on the Saffir-Simpson Wind Scale. The TRMM and GPM satellites, ...

The fires superimposed on the satellite image of southeastern Australia designated by red spots may be indicative of "planned burns" by the Victoria region. This map: http://www.depi.vic.gov.au/fire-and-emergencies/planned-burns/planned-burns-now-and-next-10-days found on the Department of the Environment and Primary Industries for the State of Victoria shows the burns th ...

New maps of global forest cover from the International Institute for Applied System Analysis (IIASA)'s Geo-Wiki team provide a more accurate view of global forests. The maps were published in the journal ...

It takes a lot of ingenuity – not to mention a massive quantity of sheer force – to get satellites into orbit. Now space engineers are applying comparable ingenuity to the challenge of getting their missions ...

One of the four Cluster satellites has shifted its orbit to ensure a safe reentry when the time comes, as well as providing a rare opportunity to study how a satellite's exhaust plume interacts with the solar ...

Tropical Cyclone Nathan has been weakening as it continued to move over land in Australia's Northern Territory on March 24. NASA's Aqua satellite captured a visible picture of the storm over land. Just one ...

Satellite

In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon.

The first artificial satellite, Sputnik 1, was launched by the Soviet Union in 1957. By 2009 thousands of satellites have been launched into orbit around the Earth. These originate from more than 50 countries and have used the satellite launching capabilities of ten nations. A few hundred satellites are currently operational, whereas thousands of unused satellites and satellite fragments orbit the Earth as space debris. A few space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Venus, Mars, Jupiter and Saturn.

Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites. Satellite orbits vary greatly, depending on the purpose of the satellite, and are classified in a number of ways. Well-known (overlapping) classes include low Earth orbit, polar orbit, and geostationary orbit.

Satellites are usually semi-independent computer controlled systems. Satellite subsystems attend many tasks, such as power generation, thermal control, telemetry, attitude control and orbit control.